Pathologic frozen and paraffin-embedded material from patients with familial multiple endocrine neoplasia type 1 (MEN 1) referred to the Clinical Center for treatment is reviewed and correlated with clinical features of disease. Tumor and normal tissue is microdissected from routine histological glass slides and the DNA is extracted and analyzed for loss of heterozygosity (LOH) on chromosome 11q13 using multiple polymorphic DNA markers spanning the area of the putative MEN 1 gene. Differential LOH patterns in multiple tumors in the individual MEN 1 patients are utilized to assist in mapping of the MEN 1 suppressor gene. This information will be used to further the understanding of the pathogenesis and early detection of multiple endocrine tumors arising in this patient population throughout their lifetime. Sporadic endocrine tumors of parthyroid, pancreatic and small bowel origin are also being investigated for 11q13 LOH to establish the role of the putative MEN 1 gene in sporadic tumorigenesis.